Originally Posted by tomthbomb
What can I expect to gain/lose?
The 730N has dead reckoning and bread crumbs, and the 430N does not. Personally, I would never use a Nav that doesn't have dead reckoning. Dead reckoning allows the Nav system to continue to successfully navigate even after loosing the GPS signal. This can happen all too easily in urban-canyons, and for me, that's just when one needs the Nav system the most.
BTW, those Garmin "stuck to the windshield" Nav units don't have dead reckoning either. I learned that the hard way. Nothing like the Garmin unit telling me, when I am in the middle of Manhattan, "GPS signal lost. No further guidance possible. Good luck."
The 730N comes with Bluetooth built-in. The 430N does not, though you can gain Bluetooth with an external box that comes with the Connectivity Package.
The 730N has Harmon based Nav system (Tom Tom like). The 430N has Garmin based Nav system, but lacks what just about every other Garmin device has, a micro-SD card slot for easy/cheap map updates. With Harmon vs. Garmin, its just a matter of personal taste of which style you like.
The 730N does split screens. I don't think the 430N does.